Abstract: Several established cancer treatments take advantage of the fact that cancer cells are often more sensitive to DNA damage from chemical and radiation treatment than non-cancer cells. One shortcoming of this approach, however, is that indiscriminant DNA damage can have toxic effects on non-cancer cells, which makes more specific therapeutics that directly target individual DNA repair proteins highly valuable. Recently chemotherapeutics that block activity of the DNA repair protein poly ADP ribose polymerase have shown great promise as more selective genomic destabilization agents. This proposal seeks to extend the range of selective chemotherapeutic DNA repair targets by developing small-molecules that block the critical interface that links two DNA repair complexes, the Fanconi Anemia core complex and the Bloom dissolvasome. We have used X-ray crystallographic, biochemical, and cell biological approaches to reveal the critical nature of this higher-order complex for cellular genomic stability. In this proposal, we will use a high-throughput chemical screen to identify protein interaction inhibitors that disrupt the Fanconi Anemia core complex/Bloom dissolvasome supercomplex. Classical biochemical and structural aproaches will be used to assess the potency and mechanisms of action of the inhibitors and to drive future rational lead improvement. The chemotherapeutic potential of the lead compounds will be determined by measuring their effects on the specific types of DNA damage repaired by the supercomplex and by assessing whether they selectively inhibit growth of cancerous human cell lines.